feat(market): historical chart intervals, stats overlay, configurable outline, easier resize

Chart:
- The price chart now plots the historical CoinGecko series with a Live/1H/1D/1W/1M
  interval selector (top-left of the chart). Live = in-session buffer; 1H uses the
  intraday 5-min series, 1D/1W/1M the daily series (via pfSparklineSeries). X-axis
  labels are interval-aware ("~5h"/"~3d"/"~2w"/"~4mo"). Market-tab open kicks the
  self-throttled market_chart fetch so history populates promptly.
- 24H volume + market cap moved from their own row onto the chart's top strip
  (right side, next to the refresh button), reclaiming the empty band above the
  chart; the hero header now holds just the price row + separator.
- More bottom padding under the plot so the time labels and the DRGX/USDT pair
  buttons aren't crowded against the card edges.

Portfolio groups:
- Accent-outline opacity is now configurable per group (0-100%, default 25%) via a
  slider in the editor's Appearance column; applied to the card + preview outline.
- Resize grip enlarged (14->20px) and a live "W x H" size readout is drawn while
  resizing, so shrinking a group to the 4x3 minimum is reliable and visible.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/config/settings.cpp

@@ -318,6 +318,8 @@ bool Settings::load(const std::string& path)
                     entry.icon = e["icon"].get<std::string>();
                 if (e.contains("color") && e["color"].is_number())
                     entry.color = e["color"].get<unsigned int>();
+                if (e.contains("outline_opacity") && e["outline_opacity"].is_number_integer())
+                    entry.outlineOpacity = e["outline_opacity"].get<int>();
                 if (e.contains("price_basis") && e["price_basis"].is_number_integer())
                     entry.priceBasis = e["price_basis"].get<int>();
                 if (e.contains("manual_price") && e["manual_price"].is_number())
@@ -493,6 +495,7 @@ bool Settings::save(const std::string& path)
         for (const auto& a : e.addresses) entry["addresses"].push_back(a);
         entry["icon"] = e.icon;
         entry["color"] = e.color;
+        entry["outline_opacity"] = e.outlineOpacity;
         entry["price_basis"] = e.priceBasis;
         entry["manual_price"] = e.manualPrice;
         entry["manual_currency"] = e.manualCurrency;

src/config/settings.h

@@ -80,6 +80,7 @@ public:
         std::vector<std::string> addresses;
         std::string icon;           // project_icons wallet-icon name; empty = no icon
         unsigned int color = 0;     // packed IM_COL32 accent; 0 = theme default
+        int outlineOpacity = 25;    // accent-outline opacity, percent (0-100)
         // Per-group price data. priceBasis: 0 = live market (USD), 1 = live market (BTC),
         // 2 = DRGX only (no fiat value), 3 = manual price. Defaults preserve prior behavior
         // (show DRGX + USD value).